The specific aims of the project include: [1] The determination of choline and citrate levels in 50 age-matched controls. Spatial resolution for this clinical 3D 1-H MRSI work will be 0.1-0.2 cc to provide a basis for determining the significant spectral differences indicative of cancer in both the peripheral zone and central gland. The MRSI data will be measured at two separate exams for each subject with the exams spaced one week apart; the aim is to establish reproducibility. [2] The correlation of choline and citrate levels with histologic grade. A total of 150 pre-prostatectomy patients will be studied, one exam each, to correlate levels of choline and citrate with step-section histopathological analysis of the excised gland. Volume estimates from the MRSI images will be compared with those from transrectal ultrasound (TRUS) and step-sectioned pathology. [3] The determination of choline and citrate levels after hormonal therapy in 50 patients with Stage C prostate cancer enrolled in a multicenter Phase II clinical trial of total hormonal ablation therapy with the LH-RH agonist Zoladex, which causes medical castration, and the anti-androgen flutamide, which inhibits androgen uptake and/or binding to the nuclear receptor. High- resolution 3-D MRI/ MRSI examinations will be performed 3 times for each patient: prior to the start of hormone therapy, at week 8 of treatment, and at week 16 of treatment just prior to prostatectomy. [4] The determination of choline and citrate levels in 50 patients approximately one year after radiation therapy. These will be patients suspected of recurrence; MRSI will be performed just prior to ultrasound guided sextant biopsies.